Double-acting hydraulic cable pulling system



Oct. 28, 1969 A. E. E. DESPLATS ET AL DOUBLE-ACTING HYDRAULIC CABLE PULIJING SYSTEM Filed rm.- 5. 1967 4 Sheets-Sheet 1 HNDRE' emu: EVRR RAYMOND vnmu n INVEI'VT'ORS ISTE DESPLRTS Mw URICE LEVA RDON TO R NEY Oct. 28, 1 969 A; i ogseLA-fs ET AL DOUBLE-ACTING HYDRAULIC CABLE PULLING SYSTEM- Filed Nov. 8. 1967 4 Sheets-Sheet UVVENTQRS ANDRE EM. zvnm 7 1969 A. E. E. D sPLATs ETAL ,474, 4

' DOUBLE.-ACTING HYDRAULIC CABLE PULLING SYSTEM Fi e News; 1967 v Sheets-Sheet 4 l l1 W uv vEN "ro Rs ANDRE EMILE EVARISTE uzs'nnrs mw' RAYMOND DANIEL MAURICE LEVARDON I nriogusvs United States Patent 01 dice 3,474,946 Patented Oct. 28, 1969 3,474,946 DOUBLE-ACTING HYDRAULIC CABLE PULLING SYSTEM Andr Emile Evariste Desplats, Boulogne-Billancourt, and Raymond Daniel Maurice Levardon, Paris, France, assignors to Tractel S.A., Paris, France, a corporation of France Filed Nov. 8, 1967, Ser. No. 681,375 Claims priority, application France, Nov. 14, 1966, 83,559; Nov. 15, 1966, 84,071; Apr. 12, 1967, 102,454; Apr. 13, 1967, 102,624

Int. Cl. B65h 17/36 US. Cl. 226-112 17 Claims ABSTRACT OF THE DISCLOSURE The double-acting hydraulic cable pulling system, wherein the cable extending through the apparatus is adapted to be gripped by a pair of self-clamping devices, is characterized by the mounting of each self-clamping device on the movable piston rod of an associated doubleacting hydraulic actuator. The two chambers of each of the two hydraulic actuators are connected to a hydraulic circuit common to both hydraulic actuators, fed from a source of fluid under pressure and provided with suitable distributor means controlling in synchronism the reverse movements of the piston rods and providing the automatic reversal of their stroke under the control of members rigid with the movable assemblies of the two actuators.

Cable pulling apparatus are already known wherein the cable extending through the apparatus is adapted to be gripped by a pair of self-clamping devices to which reverse and alternate reciprocal motions are imparted so as to clamp the cable and pull same in the direction of the desired cable traction and release the cable during the clamp stroke in the opposite direction by allowing the clamp to slide along the cable, these clamps resuming their clamping action at a farther point of the cable, so that at each stroke the cable is pulled by one or the other clamp, i.e. the one moving in the direction of the desired pulling eflort.

Reversing the cable clamping and release sequence through suitable control means will further permit the backward movement of the cable pulled by a load, so that this load will be allowed to recede while being retained in a controlled manner.

In known apparatus of this general type the clamps are actuated as a rule by mechanical control means usually reversed by hand upon completion of each stroke. Various arrangements for driving said control means by means of a mechanical motor have already been proposed but so far only cumbersome, complicated, costly and unreliable constructions have been obtained.

On the other hand a single-acting hydraulic control apparatus has also been proposed which comprises a single movable and reciprocable clamp and a fixed clamp, wherein a return stroke without any tractive action or backward movement of the cable was necessary between two successive working strokes.

It is the object of the present invention to provide hydraulic control means adapted to operate according to the double-action principle, i.e. the cable being alternately pulled by both clamps, and also to produce the clamp stroke reversal in a fully automatic manner.

To solve the problem set forth hereinabove the present invention provides a double-acting cylinder and piston unit or hydraulic actuator associated with each clamp and secured in the apparatus with the clamp mounted on the outer end of the relevant piston rod, the two chambers of each actuator being connected to a hydraulic circuit common to both actuators, fed from a source of fluid under pressure and provided with suitable distributor means controlling in synchronism the reverse movements of the piston rods and providing the automatic reversal of their stroke under the control of members rigid with the movable assemblies of the two actuators.

To permit the controlled backward movement of a loaded cable by means of the same apparatus this invention further provides an auxiliary double-acting actuator for controlling the clamping and release of each cable clamp, these hydraulic actuators having their four chambers connected to a branch line of the hydraulic circuits of the main actuators which is so arranged as to release the clamp moving in the direction opposite to the direction of pull of the load while clamping the other cable clamp.

This invention further provides means adapted, upon each reversal of the clamp movements, to transfer the load from the clamp to be released to the clamp to be closed while preventing the clamp to be opened from freeing the load-supporting cable before the clamp to be closed exerts a clamping effort sufiicient to retain said loaded cable.

Specific means may be provided for causing this load transfer step to take place without introducing any pause in the traction or in the backward movement, whereby a continuous traction and/or backward movement can be obtained in spite of the reversal of the clamp movements.

Finally, this invention contemplates the use, for producing said backward movement, of means adapted to recover the power released during the backward movement of the load for operating the necessary control devices without resorting to any external source of power such as a source of hydraulic fluid under pressure.

In order to afford a clearer understanding of this invention a few typical and preferred forms of embodiment thereof will now be described with reference to the accompanying drawings in which:

FIGURE 1 is a simplified diagram showing the clampactuating cylinder and piston units or hydraulic actuators anlgl the hydraulic circuits required for pulling a loaded ca 1e;

FIGURE 2 is a similar diagram showing the hydraulic circuits required for producing the controlled backward movement, certain details of the assembly shown in FIG- URE 1 being omitted for the sake of clarity;

FIGURE 3 is a diagram showing a modified form of embodiment of the hydraulic circuits for pulling a cable to be driven with a continuous motion; and

FIGURE 4 is a diagram showing a modified form of embodiment of the hydraulic circuits contemplated for obtaining a continuous backward movement without consuming hydraulic fluid under pressure, for example from a power driven pump.

The various means described hereinafter with reference to the drawings may be combined in different manners or used separately or in any suitable combination in self-clamping apparatus other than those illustrated. More particularly, the means contemplated herein for transferring the load from one clamp to another may also be used in a single-acting apparatus, i.e. wherein a single clamp is movable in the cable traction direction.

Some of the means contemplated herein for pulling the cable in the traction direction may be designed to operate only in this direction, for example in arrangements wherein the backward operation is not necessary.

The hydraulic cable traction apparatus according to this invention as illustrated diagrammatically in FIG- URES 1 and 2 of the drawings comprises a pair of tandem-disposed self-clamping cable clamps 1, 2 secured to the outer ends of tubular rods 3, 4 rigid with the pistons 5, 6 of a pair of cylinders 7, 8 of tandem-mounted hydraulic actuators, and solid with a common anchor member or body. The clamps 1, 2 are adapted to grip a same cable (not shown) extending through the apparatus and passing through the aligned tubular piston rods 3, 4 and also through tubular extensions (not shown) emerging from the cylinder bottoms; this cable is assumed to carry a load at its end emerging from the apparatus on the right-hand side thereof as seen in these figures. Each piston 5, 6 divides the corresponding cylinder 7, 8 into two chambers, i.e. a chamber 9, 10 on the piston side opposite to the rod and referred to hereinafter as the trust chamber, and a chamber 11, 12 surrounding the tubular rod and referred to as the traction chamber.

The thrust chambers 9, 10 are interconnected by a pipe line 13 communicating with the monitoring circuit 14 having a function to be explained presently.

Each traction chamber 11, 12 is connected on the one hand to the outlet of a non-return valve 15, 16 associated with each chamber and on the other hand to the inlet of a exhaust valve 17, 18 also associated with each chamber. Each valve 17, 18 is urged to its closed position by a spring 19, 20 and adapted to be opened by the antagonistic pressure of a fluid supplied via a hydraulic monitoring pipe line 21, 22. Each hydraulic monitoring pipe line 21, 22 is adapted to be connected by means of a distributor 23, 24 either (in the inoperative position of the relevant distributor) to the exhaust line 25, 26 leading to the reservoir or (in the operative position of said distributor) to the monitoring circuit 14. Each distributor 23, 24 is urged to its inoperative position by a corresponding spring 27, 28 and adapted to be brought to its operative position by the antagonistic action of the fluid pressure in a monitoring circuit 29, 30 connected to the inlet of the non-return valve 16, 15 associated with the opposite actuator.

The inlets of non-return valves 15, 16 are connected respectively to a pair of ports of a two-position reversing distributor 31 having another pair of ports connected to the hydraulic pressure supply circuit 32 and to a line 33 leading to the reservoir, respectively. The pressure circuit 32 is connected directly to a monitoring cricuit 34 adapted to be connected to either of a pair of monitoring lines 35, 36 of the reversing distributor via one of a pair of distributors 37, 38. These are responsive to the movable assemblies 1, 3, 5 and 2, 4, 6 respectively of the main actuators, against the antagonistic resistance of a return spring, when these assemblies complete their inward stroke (i.e. to the left as seen in the figure). Controlling one of the distributors 37, 38 will cause the corresponding monitoring pipe line 35, 36 to communicate with the monitoring circuit 34 under pressure, and when the same distributor 37, 38 is returned to its inoperative position the same monitoring pipe line is connected to the exhaust and therefore to the reservoir.

The above-described component elements of the apparatus are common to FIGURES 1 and 2 and operate in the same manner both in the traction and backward direction for controlling the movements of the movable clamps, but to simplify the disclosure the operation obtaining for pulling the cable will firstly be described in detail. For a proper understanding of this specific cable operation reference will be made only to FIGURE 1 in which the circuits controlling the closing and opening actions of the clamps necessary for producing the backward movements have been omitted.

Each self-clamping clamp 1, 2 comprises in a manner already known per se a clamp body rigid with the tubular piston rod 3, 4 and carrying a pair of opposite jaws (not shown) by means of mechanical members providing a self-clamping action and such that a relative movement of the jaws to the right (as seen in the figure) in relation to the clamp body, for example as a consequence of the pull exerted by the loaded cable, will exert on the cable a clamping force increasing with the pull or load. Under these conditions it is clear that any movement of 4 the clamp to the left (as seen in FIGURE 1) will grip and therefore pull the cable. In contrast thereto, any movement of any one clamp to the right (while the other clamp holds or pulls the cable) will release the first clamp and cause same to slide along the cable.

The positions illustrated in FIGURE 1 are those obtaining when the clamp 1 moves to the left and pulls the cable, while the other clamp 2 moves to the right by sliding along the cable.

During the stroke described hereinabove the chamber 11 is fed from circuit 32 via distributor 31 and non-return valve 15, and piston 5 therefore moves to the left (as seen in the figure) and the hydraulic fluid contained in chamber 9 is transferred via pipe line 13 to chamber 10, piston 6 sliding to the right while chamber 12 dis- 12 discharged through valve 18 opened by the fluid pres sure in the relevant monitoring pipe line 22 communicating with the aforesaid line 13 interconnecting cham bers 9 and 10, due to the action of distributor 24 responsive to the monitoring pressure prevailing in pipe line 30 connected to chamber 11. The low pressure obtaining in chamber 12 is transmitted to the monitoring pipe line 29 of distributor 23 and the latter is therefore returned by its spring 27 to the position causing the monitoring pipe line 21 of valve 17 to communicate via pipe line 25 with the reservoir, whereby this valve 17 is allowed to be reseated by its spring 19. Both monitoring pipe lines 35, 36 of the reversing distributor are connected to the reservoir via distributors 37, 38 returned to their inoperative positions by their relevant springs.

It will be noted that piston 6 cannot travel faster than piston 5 for the pressure drop produced thereby in pipe lines 13 and 14 would cause the valve 18 to be reseated by its spring, thus preventing the chamber 12 from being discharged and causing piston 6 to slacken. Then the pressure in pipe line 13 increases and causes the opening of valve 18.

When the rod 3 has completed its inward stroke the movable assembly 1, 3, 5 actuates the distributor 37, thus isolating the reservoir from the monitoring pipe line 35 of reversing distributor 31 and connecting said reservoir to the pressure line 34. Under these conditions the pressure in line 35 will move the sliding member of reversing distributor 31 to the right, i.e. to the position shown in FIGURE 2 while reversing the fluid connections previously provided by this distributor; in other words, the inlet of non-return valve 16 and monitoring circuit 29 are now connected to the fluid pressure source 32 and the inlet of non-return valve 15 and monitoring circuit 30 are connected to the reservoir. Thus, the supply of fluid to chamber 11 is discontinued and the cable movement is stopped, but chamber 12 is fed with hydraulic fluid since the output of valve 16 is greater than that of exhaust valve 18, by construction. The pressure increment in chamber 12 will move piston 6 to the left to close the clamp 2 and thus retain the cable, while the hydraulic fluid pressure increases in chambers 10 and 9, this increment being still greater in chamber 12. When a predetermined fluid pressure is attained in chamber 12 the distributor 23 is actuated to direct the pressure in circuit 14 (i.e. the pressure produced in chambers 10 and 9) to valve 17 whereby, for a given pressure valve in chamber 10, valve 17 begins to open, thus permitting the movement of piston 5 to the right (as seen in the figure) to start the outward movement of the movable assembly 1, 3, 5 as a consequence on the one hand of the fluid pressure in chamber 9 and on the other hand of the residual load still urging the clamp 1 at this time before the load is fully transferred to the other clamp 2.

The speed at which the load causes the clamp 1 to recede during the reversal is thus kept at a value equal to the speed at which the piston 6 is caused to move towards the bottom of the relevant cylinder by the action of valve 17 the opening of which is controlled by the pressure prevailing in circuit 13, 14.

When it is desired to operate the apparatus in the opposite direction (i.e. towards the load or to the right as seen in FIGURE 2) the additional members shown in this figure are used, as will now :be described in detail.

Two cylinders of a pair of auxiliary hydraulic actu ators 39, 40 are rigid with the cylinders of the main actuators 7 and 8 respectively, and provided with pistons 41, 42 rigid with rods 43, 44 pivotally connected to levers 45, 46 controlling the closing of the clamp jaws. In the example illustrated in the drawing the clamp jaws are so mounted that the movement of these rods 43, 44 to the right as seen in the figure, in relation to the clamp bodies 1 and 2, tends to close these clamps, and that the movement of rods 43, 44 in the opposite direction in relation to the clamp bodies 1 and 2 tend to open said clamps. These pistons 41, 42 divide the cylinders 39, 40 into two chambers 47, 49 (cylinder 39) and 48, 50 (cylinder 40). Chambers 47 and 48 communicate with each other via a pipe line 51, and chambers 49 and 50 are connected to the inlets of the non-return valves 15 and 16 respectively.

The positions illustrated in FIGURE 2 correspond to a movement to the right of the right-hand clamp 1 gripping the cable with its jaws, so that this clamp will move bodily with the cable during its backward movement, and to a movement to the left of clamp 2, then open and sliding freely on the cable.

In the inoperative condition the load is distributed uniformly among the two clamps 1 and 2 retained thereby due to their self-clamping action, and the two exhaust valves 17, 18 are closed. The simultaneous building up of pressure in chambers 12 and 50 on the side of rods 4 and 44 will firstly bring the distributor 23 to the position illustrated and release clamp 2, the piston 6 remaining stationary and the loaded cable being henceforth retained by the still stationary clamp 1. Then the pressure produced in chamber 12 of the main actuator causes on the one hand the movable assembly 2, 4, 6, 44, 42 controlling clamp 2 to move to the left, and on the other hand piston 42 to increase the fluid pressure in the connecting line 51, thus incrementing the clamping action of clamp 1 due to the right-hand thrust exerted by piston 41, while piston 6 tends to force the fluid from chamber to chamber 9 of actuator 7 via line 13. As the piston 5 is stationary the pressure rises in line 13 up to a certain value whereat valve 17 begins to open due to the monitoring pressure created in circuit 14 and transmitted via distributor 23. The opening of this exhaust valve 17 causes the chamber 11 to communicate with the reservoir while throttling the fluid flow and thus keep to a constant rate the backward movement of the cable which is due to the now permissible movement of piston 5 to the right. Any tendency of piston 5 to accelerate its movement creates a relative cavitation in circuit 13, 14 by reducing the cross-sectional passage area of valve 17 monitored by the fluid pressure in this circuit, whereby the operation of this valve will prevent or counteract any variation in the backward speed of the cable.

Upon completion of the inward stroke of clamp 2 the actuation of the distributor 38 will reverse the position of distributor 31 by means of the pressure built up in the monitoring circuit controlled by the distributor 38, and the supply pressure is then applied to chambers 11 and 49 by producing an effort similar to those described hereinabove in connection with the pressurizing of chambers 12 and 50 but with a permutation of the clamps to which these efforts are applied. It will be noted that during the reversal the pressure at the inlet end of the non-return -valve actuates the distributor 24 whereby the valve 18 becomes responsive to the monitoring circuit 13, 14, while chambers 11 and 49 are supplied with fluid to release clamp 1 and close clamp 2 both by self-clamping action and by transfer of fluid from chamber 47 to chamber 48, When the clamp 1 has been released sufliciently this clamp 1 can slide freely along the cable in the forward direction (i.e. away from the load and to the left as seen in the figure), the pressure rises in circuit 13, 14, valve 18 is progressively opened and connects chamber 12 to the reservoir, thus controlling the outward motion speed of the movable assembly 2, 4, 6, 44, 50. At the end of this in:- ward stroke of clamp 1 the distributor 37 is actuated to feed the monitoring circuit the pressure of which will restore the reversing distributor 31 to the position shown in FIGURE 2, and the cycle of operations is repeated as long as the supply 32 is maintained. If this supply 32 is cut ofii, pistons '6 and 42 are stopped, and piston 5, by continuing its movement to the right, creates in circuit 13, 14 a vacuum permitting the closing of valve 17 and consequently holding the clamp 1 against movement, this clamp remaining closed however due to the connection of chamber 49 to the reservoir.

, It is clear that the apparatus can be switched from traction operation to backward operation, or vice versa, by

- actuating a manual reversing switch (not shown) adapted to connect on or cut off, according to the specific case contemplated, the pipe lines supplying chambers 49 and 50.

In the above-described apparatus a certain pause is observed in either direction (traction or backward motion) upon each reversal of the movements performed by the clamps, which are symmetrical. However, if desired, and as will now be disclosed with reference to FIGURES 3 and 4, a continuous traction or backward motion may be obtained, provided that the movement of the released clamp be reversed before the movement of the other clamp, and closed during its movement in the same direction as the other clamp which is being released, means being provided for transferring the load from the previously closed clamp to the previously open one. Furthermore, specific means according to this invention for producing the backward movement without resorting to any external source of power, i.e. by recovering one fraction of the energy produced by the backward movement of the load, will also be described with reference to FIGURE 4 of the drawings.

In the specific form of embodiment illustrated in FIG- URE 3 the hydraulic cable-pulling apparatus according to this invention comprises a pair of cable actuators 61, 62 rigid with a same and common anchoring point. Pistons 63 and 64 divide the cylinders of these actuators into variable-volume chambers 65, 67 and 66, 68 and are respectively rigid with rods 69 and 70 carrying at their outer ends corresponding self-clamping cable clamps 71, 72 equipped with jaws 73 and 74 adapted to engage the cable 56, the movable assemblies, consisting on the one hand of members 63, 69, 71 and on the other hand of members 64, 70, 72, being solid with load transfer control devices 75 and 76, respectively. A valve 77 connected to the chambers 65 and 67, of unequal cross-sectional dimensions, of actuator 61, is adapted to interconnect or isolate these two chambers, and a valve 78 is provided for performing the same function with respect to chambers 66 and 68 of actuator 62.

It will be noted that the chambers 67 and 63 of actuators 61 and 62, which are remotest from the cable load, have a greater cross-sectional dimension than chambers 65 and 66 of which the cross-sectional area may advantageously be reduced by properly proportioning the outer diameter of rods 69 and 70. A switching valve 57 having two positions 79 and 80 is adapted in position 80 to connect the bottom chamber 68 of actuator 62 to the inlet of an exhaust valve 52 calibrated by a spring 53, and in position 79 to connect the bottom chamber 67 of actuator 61 to the inlet of said discharge valve 52.

A distributor 54 having three positions 58, 59, 60 is adapted to provide the following fluid connections: in its endmost position 58 the distributor 54 connects on the one hand the pressure fluid supply circuit 55 to chamber 65 on the rod-side of actuator 61 via a non-return valve 81 and on the other hand the bottom chamber 67 of actuator 61 to the rod-side chamber 66 of actuator 62 via a non-return valve 82; in its other endmost position 59 the distributor 54 connects on the one hand the pressure fluid supply circuit 55 to chamber 66 of actuator 62 via the aforesaid non-return valve 8-2 and on the other hand the chamber 68 of actuator 62 to chamber 65 of actuator 61; in its intermediate position 60 the distributor 54 connects the fluid pressure supply circuit 55 to both chambers 65 and 66 of actuators 61 and 62 through said valves 81 and 82.

A monitoring distributor 83 having two positions 85 and 87 is adapted to create the following fluid connections: in its normal position 85 (to which it is urged by a return spring 89) this distributor 83 connects to the reservoir on the one hand the pressure-monitoring circuits 93 and 96 for opening valve 77 and closing valve 78, respectively, and on the other hand the rod-side chamber 66 of actuator 62 to the pressure-monitoring circuit 98 of switching valve 57 to move this valve to its position 79; in its other position 87 resulting from the action of a projection 75 carried by clamp 71 on the distributor control member 91, thus distributor 83 will connect the monitoring circuit 96 to the pressure circuit 55 and the monitoring circuit 93 to an intermediate circuit 107 connected in turn to an auxiliary outlets of distributor 54. In its position 59 this distributor 54 will connect the aforesaid intermediate circuit 107 to the pressure circuit 55. A monitoring distributor 84 having two positions 86 and 88 is adapted, through the medium of valves 77, 78 and 57 and via monitoring circuits 94, 95, 97 and 108 similar to circuits 93, 96, 98 and 107, respectively, of distributor 83, to produce monitoring actions opposite to those generated by means of the same valves by said monitoring distributor 83 when distributor 84 is in positions corresponding to those of distributor 83 but at different times. In position 58, the distributor 54 will connect circuit 108 to the pressure fluid supply circuit 55.

A two-position valve 99 comprising two monitoring devices 101 and 103 having proportional cross-sectional areas is adapted in its position wherein the action of the small monitoring cross-sectional area 101 is predominant, to connect the pressure fluid circuit 55 to the monitoring circuit 105 of distributor 54 for switching same to its other position 58; in its other position, wherein the action of the large monitoring cross-sectional area 103 is predominant, said valve 99 connects the monitoring circuit 105 to the reservoir. The small monitoring section 101 is connected to the chamber 65 of actuator 61 and the large monitoring section 103 is connected to the chamber 67 of the same actuator. Another valve 100 identical with valve 99 and comprising monitoring circuits 102, 104 and 106 similar to circuits 101, 103 and 105 of valve 99 is responsive to the pressure obtaining in chambers 66 and 68 of actuator 62 and produces on said distributor 54 monitoring actions which are opposite to but not simultaneous with those produced by the valve 99 on the same distributor 54.

It is clear that it would not constitute a departure from the scope of the invention to bring various modifications in the above-described forms of embodiment. Thus, notably, the hoisting or traction actuators may be disposed indifferently in series, in parallel, in series-parellel, and the device may comprise if desired several pairs of actuators connected by pairs to the clamps acting upon the cable 56, these clamps being of any desired and known type.

Now the operation of the apparatus will be described by assuming that the cable is attached to a load at its left-hand end. In the position shown in FIGURE 3, the movable assembly of actuator 61 is moving inwards of the cylinder and the movable assembly of actuator 62 is moving outwards. During its inward stroke the piston 63 forces the fluid out from chamber 67 via distributor 54 to actuator 62 which, due to its connection through valve 78, operates as a differential actuator; therefore, the movable assembly of actuator 62 will move outwards at a faster rate than the inward movement of the movable assembly of actuator 61 pulling the cable 56 by means of its associated clamp 71, the other clamp 72 sliding freely along the cable 56. When the piston 64 has completed its outward stroke the other piston 63 continues its forward travel and forces the fluid out from chamber 67 towards the reservoir, via valve 57 and exhaust valve 52.

Before completing its stroke the projection 75 of clamp 71 actuates the member 91 controlling the monitoring distributor 83, thus cutting olf the fluid connection previously established by valve 78 as a consequence of the monitoring action transmitted through line 96; chamber 66 and 68 are isolated from each other, the fluid in chamber 67 cannot escape to the reservoir and the fluid pressure rises in chamber 66; the inward stroke of piston 64 begins while the jaws 74 of clamp 72 are gradually closed on cable 56. When a predetermined pressure is attained in chambers 67 and 66, valve is controlled by the monitoring device 102, whereby a monitoring pressure is built up in circuit 106; as the monitoring pressure in line is the same but of opposite direction as that generated in line 106, the distributor 54 remains in its position 58; a further pressure increment in chambers 67 and 66 will cause the valve 99 to be monitored by its large-section monitoring device 103; under these conditions, the line 105 of distributor 54 is connected to the reservoir, the pressure in circuit 106 causing the distributor 54 to resume its intermediate position 60 in which the pressures in chambers 65 and 66 become equal while chamber 67 is isolated, thus holding the piston 63 against movement; then distributor 54 reaches its position 59 which, while maintaining the supply of fluid to chamber 66, causes on the one hand the monitoring of valve 77 to open and thus to interconnect chambers 65 and 67, and on the other hand the chamber 68 to be in fluid connection with chamber 65; thus, the movable assembly of actuator 61 is moved outwards at high speed as it is supplied under differential operating conditions by chamber 68; when distributor 83 has resumed its inoperative position 85, the pressure in chamber 66 controls via pipe line 98 the switching valve 57 to its position 79 to connect chamber 67 to the exhaust valve 52. When the movable assembly of actuator 62 has nearly completed its inward stroke, its projection 76 engages the control member 92 of monitoring distributor 84, thus starting the load transfer process and the reversal of the clamp movement, as in the preceding case but in the reverse order, whereby the loaded cable is driven with a continuous, uniform motion.

In the other exemplary form of embodiment illustrated in FIGURE 4 the apparatus still includes the members 61 through 74 described hereinabove in connection with FIGURE 3, and the operation of the apparatus under the cable traction conditions will be substantially the same as that described, but to simplify the drawing and the disclosure this FIGURE 4 includes only the component elements and the fluid circuits necessary for producing the backward movement of the loaded cable. In FIGURE 4, it is assumed that the load is attached to the end of cable 56 which is on the right-hand side of the figure.

The movable assemblies consisting of elements 63, 69 and 71 on the one hand and 64, 70 and 72 on the other hand are rigid with load transfer control members 111 and 112 respectively. The clamp 71 carries a device 113 for altering the gripping action of jaws 73, and the other clamp 72 comprises a similar arrangement 114. A pair of auxiliary actuators 115 and 116 having their cylinders rigid with the cylinders of actuators 61 and 62 respectively comprise pistons 117 and 118 forming in each actuator variable-volume chambers 119, 121 and 120, 122 respectively, piston 117 being rigid with a rod 123 attached to said device 113 while piston 118 is rigid with a rod 124 attached to the other device 114. The chambers 67 and 68 actuators 61 and 62 are interconnected by a pipe line. Chamber 65 of actuator 61 is connected to the inlet of an output regulation valve 125 having its output connected to the inlet of a pressure reducing valve 127 to a connecting valve 133. The outlet of this non-return valve 133 is connected to the chamber 121 of actuator 115; the outlet of pressure reducing valve 127 is connected via another non-return valve 131 to the chamber 66 of actuator 62; the connecting valve 151 is adapted, at proper times, to connect the outlet of the output regulation valve 125 to a hydropneumatic accumulator of reservoir 153. The chamber 121 of actuator 115 is connected via a non-return valve 135 to the chamber 65 of actuator 61; the chamber 119 of actuator 115 is connected via a non-return valve 137 to the chamber 122 of actuator 116. The pressure reducing valve 127 comprises, in addition to its calibration spring 129, an additional positive control member for opening this valve to the monitoring circuit 149; the connecting valve 151 comprises a monitoring device having proportional cross-sectional areas, i.e. a large monitoring area 155 for opening the valve, a spring 157 and a pair of small independent monitoring sections 159 and 161 for closing said valve. A distributor 139 having two positions 141 and 143 provides the following fluid connections: in its normal position (to which it is urged by spring 145) it connects on the one hand the chamber 121 of actuator 115 to the chamber 120 of actuator 116 and, on the other hand, the monitoring circuit 149 of valve 127 to the hydro-pneumatic reservoir 153 shown diagrammatically in the drawing by an outlet on the right-hand side of the distributor; in its position 143 and due to the action of projection 111 of clamp 71 on its control member 147 this distributor 139 connects the monitoring circuit 149 to the chamber 65 of actuator 61. The small monitoring cross-sectional area 159 of connecting valve 151 is connected to chamber 65 of actuator 61.

The first series of means described hereinabove and comprising notably valves 125, 127, 151, non-return valve 131, 133, 135 and 137, distributor 139 and hydropneumatic accumulator or reservoir 153 is completed by another series of means having the same description as the preceding ones, which are denoted by the reference numerals 126, 128, 152, 132, 134, 136, 138, 140 and 154, respecively, all these means being connected with each other on the one hand and to the actuator chambers, on the other hand, whereby the fiuid connections provided by this second series be those obtained by replacing in the above description of the connections provided by the first series each element by an element designated by a reference numeral plus one unit.

The small cross-sectional monitoring area 161 of connecting valve 151 is connected to the additional monitoring circuit 150 of valve 128, and the large cross-sectional monitoring area 155 of valve 151 is connected to the outlet of the output regulation valve 126; similarly, the small cross-sectional monitoring area 162 of connecting valve 152 is connected to the additional monitoring circuit 149 of valve 127, and the large cross-sectional monitoring area 156 of valve 152 is connected to the outlet of the output regulation valve 125.

Now the operation of the apparatus under backward motion condition will be described. When the piston rod 70 is moved outwards and carried along by the cable '56, the chamber 119 is supplied with fluid under a reduced pressure through valves 126, 134 and 140; piston 117 releases or opens the clamp 71 which is thus allowed to slide along cable 56 towards the actuator 61. Before the outward stroke is completed, the corresponding projection 112 actuates the distributor 140, thereby cutting off on the one hand the supply of pressure fluid to chamber 119, and on the other hand, through the action exerted by the monitoring circuit 150, the connection previously established by valve 151, by opening the valve 128 completely; thus, clamp 71 is closed to grip the cable 56 while the pressure rises in chamber 65 and decreases in chamber 66. When the pressure in chamber 65 has attained a predetermined value, the larger cross-sectional monitoring area 156 connected to the outlet 125 opens the valve 152 and thus connects chamber 66 to the hydro-pneumatic reservoir 154 through the output regulation valve 126; thus, the fluid pressure drops in chamber 66 while chamber 65 feeds chamber through valve 133 and distributor 139, thus releasing or opening the other clamp 72; at this time the two piston rods 69 and 70 move out- Wards at the same uniform speed. When the pressure in chamber '66 has attained a sufliciently low value the cable 56 begins to slide in clamp 72 while the hydro-pneumatic reservoir 154 discharges itself in chamber 66 and causes the piston rod 70 to move inwards idly on a certain stroke; when the pressure in reservoir 154 has resumed its initial value, which is the pressure necessary to cause the idly return stroke of assembly 72, 70, 64, the pressure reducing valve 127 is opened to communicate the fluid pressure of chamber 65 to chamber 66 via the output regulation valve and the movement is thus continued until the projection 111 actuates the distributor 139, thus causing another transfer of the cable load from clamp 71 to clamp 72 by reversing the clamp movements in a manner similar to that described hereinabove.

It is clear that the few forms of embodiment described hereinabove and illustrated in the accompanying drawings are given by way of examples only and that the same general means contemplated herein for automatically controlling the apparatus in the traction and backward directions could be embodied in various constructional forms without departing from the basic principles of the invention. Thus more particularly, the auxiliary actuators have been shown in the drawings as mounted side by side with respect to the main actuators, but it is also possible to incorporate each auxiliary actuator in the cylinder of the relevant main actuator which would then comprise two successive or tandem pistons having coaxial rods, one piston rod beind rigid with the clamp body and the other adapted to control the jaw closing and opening movements.

What We claim is:

1. A hydraulic double-acting cable traction apparatus comprising a body through which extends a cable, a pair of double-acting hydraulic actuators (7, 8; 61, 62) rigid with said body, movable pistons (5, 6; 63, 64) dividing each of said actuators in two chambers (9, 11; 10, 12; 65, 67; 66, 68), movable piston rods (3, 4; 69, 70) rigid With said pistons, a pair of self-clamping clamps 1, 2; 73, 74) rigid with the outer ends of said piston rods and including actuating members, a hydraulic circuit common to both actuators (7, 8; 61, 62) connected to said two chambers of each said actuator, a source of fluid (32, 55) connected in turn to said, two chambers of each said actuator,

and distributors (37, 38; 83, 84; 139, actuated by said actuating members controlling in synchronism the movements in opposite directions of the movable piston rods and causing the automatic reversal of the stroke of said piston rods.

2. Hydraulic apparatus according to claim 1, wherein the two actuator chambers (9, 10) of which the fluid pressures are exerted against the relevant pistons towards the load are directly interconnected and a fluid pressure is ap plied to one of the other two actuator chambers (11, 12) and the fourth chamber is open to a non-pressurized circuit only when the pressure in the two interconnected chambers attains a predetermined value, the supply of fluid to and exhaust of fluid from the aforesaid other two chambers (11, 12) being reversed between these two chambers each time the clamp movements are reversed.

3. Hydraulic apparatus according to claim 1, adapted to permit the controlled backward movement of the loaded cable, which comprises a pair of self-clamping movable clamps (1, 2) adapted to perform opposite reciprocating movements, each clamp being mounted on the movable piston rod (3, 4) of a double-acting power actuator and having a member (45, 46) for controlling the clamp closing and opening movements, which is operatively connected to the relevant movable piston rod (43, 44) of a double-acting auxiliary actuator, two chambers (49, 50) of these auxiliary actuators being connected respectively to the supply and return lines of the hydraulic circuit in order to control the release of the clamp moving in a direction opposite to the direction of pull of the load and to close the other clamp on the cable.

4. Hydraulic apparatus according to claim 3, wherein the fluid supply pressure is applied to the release chamber (49, 50) of the auxiliary actuator of the clamp to be released, the two clamping chambers (47, 48) of said auxiliary actuators being constantly interconnected and the fourth chamber is connected to the reservoir of the hydraulic circuit while maintaining the relevant clamp in its closed or cable-gripping position.

5. Hydraulic apparatus according to claim 1, adapted to exert a continuous, uniform traction on the cable during a reversal of the clamp movements, characterised in that each clamp, before completing its traction stroke, is adapted to actuatea distributor (83, 84) controlling the reversal of the movement of the other clamp and subsequently close same while the first clamp completes its stroke and is released.

6. Hydraulic apparatus according to claim 5, wherein each actuator comprises two chambers of unequal crosssectional area, the smaller chamber being on the load side and both chambers are interconnected by a connecting valve (77, 78) to permit a differential operation of the actuator and the return of the loaded clamp towards the load at a faster rate than the forward movement of the closed clamp exerting a traction on the cable.

7. Hydraulic apparatus according to claim 6, wherein a switching valve (57) interconnects the larger actuator chamber moving the relevant clamp back towards the load to an exhaust valve (52) adapted to open automatically when a predetermined pressure is overstepped.

8. Hydraulic apparatus according to claim 6, wherein a three-position distributor (54) connects the larger chamber of the actuator moving the relevant clamp in the traction direction to the smaller chamber of the other actuator.

9. Hydraulic apparatus according to claim 8, wherein the intermediate position of said three-position distributor is adapted to connect simultaneously the small chambers of said actuators to the circuit supplying hydraulic fluid under pressure.

10. Hydraulic apparatus according to claim 7, wherein the distributors (83, 84) actuated by said clamps are adapted to modify the positions of said connecting valves (77, 78) and switching valve (57).

11. Hydraulic apparatus according to claim 8, wherein the three-position distributor (54) is responsive to monitoring circuits (105, 106) controlled in turn by hydraulic monitoring valves (99, 100) connected for each valve to the two chambers of the actuator corresponding to said valve.

12. Hydraulic apparatus according to claim 1, adapted .to produce a continuous, uniform backward movement during a reversal of the clamp movements, characterised in that each clamp is adapted, before completing its backward stroke, to actuate a distributor (139, 140) controlling in turn the closing of the other clamp then the reversal of the movement thereof while the first clamp completes its stroke and is being released, the jaws of each clamp being controlled by an auxiliary actuator (115, 116) associated with the main actuator (61, 62).

13. Hydraulic apparatus according to claim 12, wherein the chambers disposed on the load side of said main clamp actuators (61, 62) are mutually connected by two groups of means comprising each an output regulator (125, 126), a pressure reducing valve (127, 128) and a nonreturn valve (131, 132).

14. Hydraulic apparatus according to claim 12, wherein the clamping chambers (121, 122) of the auxiliary actuators (115, 116) are connected respectively through nonreturn valves (135, 136) to the chambers located on the load side of the corresponding main actuators.

15. Hydraulic apparatus according to claim 12, wherein the non-return valves (137, 138) connect each release chamber of an auxiliary actuator to the clamping cham ber of the other actuator.

16. Hydraulic apparatus according to claim 1, adapted to permit the backward movement of the load without resorting to any external source of hydraulic fluid under pressure, wherein each actuator or group of actuators is associated with a low pressure hydro-pneumatic reservoir (153, 154) constituting a relative decompression chamber for the small chamber of the actuator which arrives at the end of its outward stroke and must transfer the load to return to the other actuator; the initial pressure into the reservoir being restored by itself when the movable assembly of the actuator, free from the load, runs inwards idly.

17. Hydraulic apparatus according to claim 16, wherein the fluid communication between each hydro-pneumatic reservoir and the chamber located on the load side in the relevant actuator through the medium of an output regulator (125, 126) is responsive to a multiple monitor-action valve (151, 152).

References Cited UNITED STATES PATENTS 2,3 89,556 11/1945 Seigerist 2261 15 2,929,626 3/ 1960 Weymouth 226-1 15 2,978,160 4/1961 Bunnell 2261 62 X ALLEN N. KNOWLES, Primary Examiner US. Cl. X.R. 

